compilation error with gcc 14

• Did you find a bug in datatable, or maybe the bug found you?

Compilation error

• How to reproduce the bug?

just compile using g++ 14.1.1

• What was the expected behavior?

compilation

• Your environment?
  dt version: 1.2.0a
  compiler: g++ 14.1.1
  os: Arch Linux kernel 6.9
  python: 3.12.4

• Tag the issue with [bug] or [segfault] (depending on whether it crashes
  Python or not).

[bug]

• Thank you for contributing, and sorry for the inconvenience.